Deletion of the P2Y2 receptor aggravates internal elastic lamina calcification in chronic kidney disease mice through upregulation of alkaline phosphatase and lipocalin-2.

Calcification of the medial layer, inducing arterial stiffness, contributes significantly to cardiovascular mortality in patients with chronic kidney disease (CKD). Extracellular nucleotides block the mineralization of arteries by binding to purinergic receptors including the P2Y2 receptor. This study investigates whether deletion of the P2Y2 receptor influences the development of arterial media calcification in CKD mice. Animals were divided into: (i) wild type mice with normal renal function (control diet) (n = 8), (ii) P2Y2 R-/- mice with normal renal function (n = 8), (iii) wild type mice with CKD (n = 27), and (iv) P2Y2 R-/- mice with CKD (n = 22). To induce CKD, animals received an alternating (0.2-0.3%) adenine diet for 7 weeks. All CKD groups developed a similar degree of chronic renal failure as reflected by high serum creatinine and phosphorus levels. Also, the presence of CKD induced calcification in the heart and medial layer of the aortic wall. However, deletion of the P2Y2 receptor makes CKD mice more susceptible to the development of calcification in the heart and aorta (aortic calcium scores (median ± IQR), CKD-wild type: 0.34 ± 4.3 mg calcium/g wet tissue and CKD-P2Y2 R-/- : 4.0 ± 13.2 mg calcium/g wet tissue). As indicated by serum and aortic mRNA markers, this P2Y2 R-/- mediated increase in CKD-related arterial media calcification was associated with an elevation of calcification stimulators, including alkaline phosphatase and inflammatory molecules interleukin-6 and lipocalin 2. The P2Y2 receptor should be considered as an interesting therapeutic target for tackling CKD-related arterial media calcification.

Endothelial dysfunction aggravates arterial media calcification in warfarin administered rats.

Arterial media calcification is an active cell process. This encompasses osteochondrogenic transdifferentiation of vascular smooth muscle cells followed by the deposition of calcium-phosphate crystals. Increasing evidence suggests a significant role for endothelial cells (ECs) in the development of arterial media calcification. This manuscript explores a role for endothelial dysfunction in the disease progression of arterial media calcification. Male rats were randomly assigned to four different groups. The first group received standard chow. The second group was given L-NAME (≈50 mg kg-1 · d-1 ), to induce endothelial dysfunction, in addition to standard chow. The third group and fourth group received a warfarin-supplemented diet to induce mild calcification and the latter group was co-administered L-NAME. Prior to sacrifice, non-invasive measurement of aortic distensibility was performed. Animals were sacrificed after 6 weeks. Arterial media calcification was quantified by measuring aortic calcium and visualized on paraffin-embedded slices by the Von Kossa method. Arterial stiffness and aortic reactivity was assessed on isolated carotid segments using specialized organ chamber setups. Warfarin administration induced mineralization. Simultaneous administration of warfarin and L-NAME aggravated the arterial media calcification process. Through organ chamber experiments an increased vessel tonus was found, which could be linked to reduced basal NO availability, in arteries of warfarin-treated animals. Furthermore, increased calcification because of L-NAME administration was related to a further compromised endothelial function (next to deteriorated basal NO release also deteriorated stimulated NO release). Our findings suggest early EC changes to impact the disease progression of arterial media calcification.

Towards a better understanding of arterial calcification disease progression in CKD: investigation of early pathological alterations.

BACKGROUND: Cardiovascular disease remains the leading cause of death in chronic kidney disease (CKD) patients, especially in those undergoing dialysis and kidney transplant surgery. CKD patients are at high risk of developing arterial media calcifications (AMC) and arterial stiffness. We hypothesized that investigation of disease progression at an early stage could provide novel insights in understanding AMC etiology. METHODS: An adenine diet was administered to male Wistar rats to induce AMC. Rats were sacrificed after 2, 4 and 8 weeks. AMC was measured by assessment of aortic calcium and visualized using histology. Arterial stiffness was measured in vivo by ultrasound and ex vivo by applying cyclic stretch of physiological magnitude on isolated arterial segments, allowing us to generate the corresponding pressure-diameter loops. Further, ex vivo arterial reactivity was assessed in organ baths at 2 and 4 weeks to investigate early alterations in biomechanics/cellular functionality. RESULTS: CKD rats showed a time-dependent increase in aortic calcium which was confirmed on histology. Accordingly, ex vivo arterial stiffness progressively worsened. Pressure-diameter loops showed a gradual loss of arterial compliance in CKD rats. Additionally, viscoelastic properties of isolated arterial segments were altered in CKD rats. Furthermore, after 2 and 4 weeks of adenine treatment, a progressive loss in basal, nitric oxide (NO) levels was observed, which was linked to an increased vessel tonus and translates into an increasing viscous modulus. CONCLUSIONS: Our observations indicate that AMC-related vascular alterations develop early after CKD induction prior to media calcifications being present. Preventive action, related to restoration of NO bioavailability, might combat AMC development.

Metformin and Canagliflozin Are Equally Renoprotective in Diabetic Kidney Disease but Have No Synergistic Effect.

Diabetic Kidney Disease (DKD) is a major microvascular complication for diabetic patients and is the most common cause of chronic kidney disease (CKD) and end-stage renal disease. Antidiabetic drugs, such as metformin and canagliflozin, have been shown to exert renoprotective effects. Additionally, quercetin recently showed promising results for the treatment of DKD. However, the molecular pathways through which these drugs exert their renoprotective effects remain partly unknown. The current study compares the renoprotective potential of metformin, canagliflozin, metformin + canagliflozin, and quercetin in a preclinical rat model of DKD. By combining streptozotocin (STZ) and nicotinamide (NAD) with daily oral N(ω)-Nitro-L-Arginine Methyl Ester (L-NAME) administration, DKD was induced in male Wistar Rats. After two weeks, rats were assigned to five treatment groups, receiving vehicle, metformin, canagliflozin, metformin + canagliflozin, or quercetin for a period of 12 weeks by daily oral gavage. Non-diabetic vehicle-treated control rats were also included in this study. All rats in which diabetes was induced developed hyperglycemia, hyperfiltration, proteinuria, hypertension, renal tubular injury and interstitial fibrosis, confirming DKD. Metformin and canagliflozin, alone or together, exerted similar renoprotective actions and similar reductions in tubular injury and collagen accumulation. Renoprotective actions of canagliflozin correlated with reduced hyperglycemia, while metformin was able to exert these effects even in the absence of proper glycemic control. Gene expression revealed that the renoprotective pathways may be traced back to the NF-κB pathway. No protective effect was seen with quercetin. In this experimental model of DKD, metformin and canagliflozin were able to protect the kidney against DKD progression, albeit in a non-synergistic way. These renoprotective effects may be attributable to the inhibition of the NF-κB pathway.

A Proteomic Screen to Unravel the Molecular Pathways Associated with Warfarin-Induced or TNAP-Inhibited Arterial Calcification in Rats.

Arterial media calcification refers to the pathological deposition of calcium phosphate crystals in the arterial wall. This pathology is a common and life-threatening complication in chronic kidney disease, diabetes and osteoporosis patients. Recently, we reported that the use of a TNAP inhibitor, SBI-425, attenuated arterial media calcification in a warfarin rat model. Employing a high-dimensionality unbiased proteomic approach, we also investigated the molecular signaling events associated with blocking arterial calcification through SBI-425 dosing. The remedial actions of SBI-425 were strongly associated with (i) a significant downregulation of inflammatory (acute phase response signaling) and steroid/glucose nuclear receptor signaling (LXR/RXR signaling) pathways and (ii) an upregulation of mitochondrial metabolic pathways (TCA cycle II and Fatty Acid ß-oxidation I). Interestingly, we previously demonstrated that uremic toxin-induced arterial calcification contributes to the activation of the acute phase response signaling pathway. Therefore, both studies suggest a strong link between acute phase response signaling and arterial calcification across different conditions. The identification of therapeutic targets in these molecular signaling pathways may pave the way to novel therapies against the development of arterial media calcification.

N-acetylcysteine (NAC) differentially affects arterial medial calcification and bone formation: The role of l-cysteine and hydrogen sulphide.

Arterial medial calcification (AMC) is the deposition of calcium phosphate in the arteries. AMC is widely thought to share similarities with physiological bone formation; however, emerging evidence suggests several key differences between these processes. N-acetylcysteine (NAC) displays antioxidant properties and can generate hydrogen sulphide (H2 S) and glutathione (GSH) from its deacetylation to l-cysteine. This study found that NAC exerts divergent effects in vitro, increasing osteoblast differentiation and bone formation by up to 5.5-fold but reducing vascular smooth muscle cell (VSMC) calcification and cell death by up to 80%. In vivo, NAC reduced AMC in a site-specific manner by 25% but had no effect on the bone. The actions of l-cysteine and H2 S mimicked those of NAC; however, the effects of H2 S were much less efficacious than NAC and l-cysteine. Pharmacological inhibition of H2 S-generating enzymes did not alter the actions of NAC or l-cysteine; endogenous production of H2 S was also unaffected. In contrast, NAC and l-cysteine increased GSH levels in calcifying VSMCs and osteoblasts by up to 3-fold. This suggests that the beneficial actions of NAC are likely to be mediated via the breakdown of l-cysteine and the subsequent GSH generation. Together, these data show that while the molecular mechanisms driving the actions of NAC appear similar, the downstream effects on cell function differ significantly between osteoblasts and calcifying VSMCs. The ability of NAC to exert these differential actions further supports the notion that there are differences between the development of pathological AMC and physiological bone formation. NAC could represent a therapeutic option for treating AMC without exerting negative effects on bone.

Progression of established non-diabetic chronic kidney disease is halted by metformin treatment in rats.

Current treatment strategies for chronic kidney disease (CKD) mainly focus on controlling risk factors. Metformin, a first-line drug for type 2 diabetes, exerts beneficial pleiotropic actions beyond its prescribed use and incipient data have revealed protective effects against the development of kidney impairment. This study evaluated the therapeutic efficacy of metformin and canagliflozin, a sodium-glucose cotransporter-2 (SGLT2) inhibitor recently approved by the United States Food and Drug Administration to treat diabetic nephropathy, in slowing the progression of established non-diabetic CKD. Rats with adenine-induced CKD were assigned to different treatment groups to receive either 200 mg/kg metformin, four or five weeks after the start of the adenine diet (established mild-moderate CKD), or 25 mg/kg canagliflozin four weeks after the start of the diet, by daily oral gavage administered during four weeks. Each treatment group was compared to a vehicle group. Chronic adenine dosing resulted in severe CKD in vehicle-treated rats as indicated by a marked rise in serum creatinine levels, a marked decrease in creatinine clearance, and a disturbed mineral metabolism. Metformin, but not canagliflozin, halted functional kidney decline. Additionally, kidneys of metformin-treated animals showed less interstitial area and inflammation as compared to the vehicle group. Proteomic analyses revealed that metformin's kidney-protective effect was associated with the activation of the Hippo signaling pathway, a highly conserved multiprotein kinase cascade that controls tissue development, organ size, cell proliferation, and apoptosis. Thus, metformin demonstrated therapeutic efficacy by halting the progression of established CKD in a rat model.

Runx2 (Runt-Related Transcription Factor 2) Links the DNA Damage Response to Osteogenic Reprogramming and Apoptosis of Vascular Smooth Muscle Cells.

[Figure: see text].

Inhibition of tissue non-specific alkaline phosphatase; a novel therapy against arterial media calcification?

Arterial media calcification refers to ectopic mineralization in the arterial wall and favors arterial stiffness and cardiovascular events. Patients with chronic kidney disease (CKD), diabetes, or osteoporosis are highly vulnerable to the development of arterial media calcifications. Tissue non-specific alkaline phosphatase (TNAP) is upregulated in calcified arteries and plays a key role in the degradation of the calcification inhibitor pyrophosphate into inorganic phosphate ions. A recent study published in The Journal of Pathology showed that an oral dosage of 10 or 30 mg/kg/day SBI-425, a selective TNAP inhibitor, inhibited the development of arterial media calcification in mice with CKD, without affecting bone mineralization. Their results indicated that SBI-425 is an effective and safe treatment for arterial media calcification. However, additional studies regarding the effect of TNAP-inhibitor SBI-425 on the progression and even the reversion of pre-existing pathological arterial media calcifications without affecting physiological bone mineralization are deserved. Furthermore, investigating the extent to which SBI-425 inhibits arterial calcification in a non-CKD context would be of particular interest to treat this comorbidity in diabetes and osteoporosis patients. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

L-NAME Administration Enhances Diabetic Kidney Disease Development in an STZ/NAD Rat Model.

One of the most important risk factors for developing chronic kidney disease (CKD) is diabetes. To assess the safety and efficacy of potential drug candidates, reliable animal models that mimic human diseases are crucial. However, a suitable model of diabetic kidney disease (DKD) is currently not available. The aim of this study is to develop a rat model of DKD by combining streptozotocin and nicotinamide (STZ/NAD) with oral N(ω)-Nitro-L-Arginine Methyl Ester (L-NAME) administration. Diabetes was induced in male Wistar rats by intravenous injection of 65 mg/kg STZ, 15 min after intraperitoneal injection of 230 mg/kg NAD. Rats were assigned to different groups receiving L-NAME (100 mg/kg/day) (STZ/NAD/L-NAME) or vehicle (STZ/NAD) for a period of 9 or 12 weeks by daily oral gavage. All rats developed hyperglycemia. Hyperfiltration was observed at the start of the study, whereas increased serum creatinine, albumin-to-creatinine ratio, and evolving hypofiltration were detected at the end of the study. Daily L-NAME administration caused a rapid rise in blood pressure. Histopathological evaluation revealed heterogeneous renal injury patterns, which were most severe in the STZ/NAD/L-NAME rats. L-NAME-induced NO-deficiency in STZ/NAD-induced diabetic rats leads to multiple characteristic features of human DKD and may represent a novel rat model of DKD.

Endothelial Contribution to Warfarin-Induced Arterial Media Calcification in Mice.

Arterial media calcification (AMC) is predominantly regulated by vascular smooth muscle cells (VSMCs), which transdifferentiate into pro-calcifying cells. In contrast, there is little evidence for endothelial cells playing a role in the disease. The current study investigates cellular functioning and molecular pathways underlying AMC, respectively by, an ex vivo isometric organ bath set-up to explore the interaction between VSMCs and ECs and quantitative proteomics followed by functional pathway interpretation. AMC development, which was induced in mice by dietary warfarin administration, was proved by positive Von Kossa staining and a significantly increased calcium content in the aorta compared to that of control mice. The ex vivo organ bath set-up showed calcified aortic segments to be significantly more sensitive to phenylephrine induced contraction, compared to control segments. This, together with the fact that calcified segments as compared to control segments, showed a significantly smaller contraction in the absence of extracellular calcium, argues for a reduced basal NO production in the calcified segments. Moreover, proteomic data revealed a reduced eNOS activation to be part of the vascular calcification process. In summary, this study identifies a poor endothelial function, next to classic pro-calcifying stimuli, as a possible initiator of arterial calcification.

Renoprotective effects of sucroferric oxyhydroxide in a rat model of chronic renal failure.

INTRODUCTION: Sucroferric oxyhydroxide (PA21) is an efficacious, well-tolerated iron-based phosphate binder and a promising alternative to existing compounds. We compared the effects of PA21 with those of a conventional phosphate binder on renal function, mineral homeostasis and vascular calcification in a chronic kidney disease-mineral and bone disorder (CKD-MBD) rat model. METHODS: To induce stable renal failure, rats were administered a 0.25% adenine diet for 8 weeks. Concomitantly, rats were treated with vehicle, 2.5 g/kg/day PA21, 5.0 g/kg/day PA21 or 3.0 g/kg/day calcium carbonate (CaCO3). Renal function and calcium/phosphorus/iron metabolism were evaluated during the study course. Renal fibrosis, inflammation, vascular calcifications and bone histomorphometry were quantified. RESULTS: Rats treated with 2.5 or 5.0 g/kg/day PA21 showed significantly lower serum creatinine and phosphorus and higher ionized calcium levels after 8 weeks of treatment compared with vehicle-treated rats. The better preserved renal function with PA21 went along with less severe anaemia, which was not observed with CaCO3. Both PA21 doses, in contrast to CaCO3, prevented a dramatic increase in fibroblast growth factor (FGF)-23 and significantly reduced the vascular calcium content while both compounds ameliorated CKD-related hyperparathyroid bone. CONCLUSIONS: PA21 treatment prevented an increase in serum FGF-23 and had, aside from its phosphate-lowering capacity, a beneficial impact on renal function decline (as assessed by the renal creatinine clearance) and related disorders. The protective effect of this iron-based phosphate binder on the kidney in rats, together with its low pill burden in humans, led us to investigate its use in patients with impaired renal function not yet on dialysis.

Indoxyl Sulfate and p-Cresyl Sulfate Promote Vascular Calcification and Associate with Glucose Intolerance.

BACKGROUND: Protein-bound uremic toxins indoxyl sulfate (IS) and p-cresyl sulfate (PCS) have been associated with cardiovascular morbidity and mortality in patients with CKD. However, direct evidence for a role of these toxins in CKD-related vascular calcification has not been reported. METHODS: To study early and late vascular alterations by toxin exposure, we exposed CKD rats to vehicle, IS (150 mg/kg per day), or PCS (150 mg/kg per day) for either 4 days (short-term exposure) or 7 weeks (long-term exposure). We also performed unbiased proteomic analyses of arterial samples coupled to functional bioinformatic annotation analyses to investigate molecular signaling events associated with toxin-mediated arterial calcification. RESULTS: Long-term exposure to either toxin at serum levels similar to those experienced by patients with CKD significantly increased calcification in the aorta and peripheral arteries. Our analyses revealed an association between calcification events, acute-phase response signaling, and coagulation and glucometabolic signaling pathways, whereas escape from toxin-induced calcification was linked with liver X receptors and farnesoid X/liver X receptor signaling pathways. Additional metabolic linkage to these pathways revealed that IS and PCS exposure engendered a prodiabetic state evidenced by elevated resting glucose and reduced GLUT1 expression. Short-term exposure to IS and PCS (before calcification had been established) showed activation of inflammation and coagulation signaling pathways in the aorta, demonstrating that these signaling pathways are causally implicated in toxin-induced arterial calcification. CONCLUSIONS: In CKD, both IS and PCS directly promote vascular calcification via activation of inflammation and coagulation pathways and were strongly associated with impaired glucose homeostasis.

The Role of Sclerostin in Bone and Ectopic Calcification.

Sclerostin, a 22-kDa glycoprotein that is mainly secreted by the osteocytes, is a soluble inhibitor of canonical Wnt signaling. Therefore, when present at increased concentrations, it leads to an increased bone resorption and decreased bone formation. Serum sclerostin levels are known to be increased in the elderly and in patients with chronic kidney disease. In these patient populations, there is a high incidence of ectopic cardiovascular calcification. These calcifications are strongly associated with cardiovascular morbidity and mortality. Although data are still controversial, it is likely that there is a link between ectopic calcification and serum sclerostin levels. The main question, however, remains whether sclerostin exerts either a protective or deleterious role in the ectopic calcification process.

Extracellular Nucleotides Regulate Arterial Calcification by Activating Both Independent and Dependent Purinergic Receptor Signaling Pathways.

Arterial calcification, the deposition of calcium-phosphate crystals in the extracellular matrix, resembles physiological bone mineralization. It is well-known that extracellular nucleotides regulate bone homeostasis raising an emerging interest in the role of these molecules on arterial calcification. The purinergic independent pathway involves the enzymes ecto-nucleotide pyrophosphatase/phosphodiesterases (NPPs), ecto-nucleoside triphosphate diphosphohydrolases (NTPDases), 5'-nucleotidase and alkaline phosphatase. These regulate the production and breakdown of the calcification inhibitor-pyrophosphate and the calcification stimulator-inorganic phosphate, from extracellular nucleotides. Maintaining ecto-nucleotidase activities in a well-defined range is indispensable as enzymatic hyper- and hypo-expression has been linked to arterial calcification. The purinergic signaling dependent pathway focusses on the activation of purinergic receptors (P1, P2X and P2Y) by extracellular nucleotides. These receptors influence arterial calcification by interfering with the key molecular mechanisms underlying this pathology, including the osteogenic switch and apoptosis of vascular cells and possibly, by favoring the phenotypic switch of vascular cells towards an adipogenic phenotype, a recent, novel hypothesis explaining the systemic prevention of arterial calcification. Selective compounds influencing the activity of ecto-nucleotidases and purinergic receptors, have recently been developed to treat arterial calcification. However, adverse side-effects on bone mineralization are possible as these compounds reasonably could interfere with physiological bone mineralization.

Sclerostin in chronic kidney disease-mineral bone disorder think first before you block it!

Canonical Wnt signalling activity is a major player in physiological and adaptive bone metabolism. Wnt signalling is regulated by soluble inhibitors, with sclerostin being the most widely studied. Sclerostin's main origin is the osteocyte and its major function is blockade of osteoblast differentiation and function. Therefore, sclerostin is a potent inhibitor of bone formation and mineralization. Consequently, blocking sclerostin via human monoclonal antibodies (such as romosozumab) represents a promising perspective for the treatment of (postmenopausal) osteoporosis. However, sclerostin's physiology and the effects of sclerostin monoclonal antibody treatment are not limited to the skeleton. Specifically, the potential roles of sclerostin in chronic kidney disease (CKD) and associated pathologies covered by the term chronic kidney disease and mineral bone disorder (CKD-MBD), which also includes accelerated cardiovascular calcification, warrant specific attention. CKD-MBD is a complex disease condition in which sclerostin antibodies may interfere at different levels and influence the multiform interplay of hyperparathyroidism, renal osteodystrophy and vascular calcification, but the clinical sequelae remain obscure. The present review summarizes the potential effects of sclerostin blockade in CKD-MBD. We will address and summarize the urgent research targets that are being identified and that need to be addressed before a valid risk-benefit ratio can be established in the clinical setting of CKD.

Metformin prevents the development of severe chronic kidney disease and its associated mineral and bone disorder.

Chronic kidney disease (CKD) causes dysregulation of mineral metabolism, vascular calcification and renal osteodystrophy, an entity called 'CKD-Mineral and Bone Disorder' (CKD-MBD). Here we determine whether metformin, an anti-diabetic drug, exerts favorable effects on progressive, severe CKD and concomitant mineral metabolism disturbances. Rats with CKD-MBD, induced by a 0.25% adenine diet for eight weeks, were treated with 200 mg/kg/day metformin or vehicle from one week after CKD induction onward. Severe, stable CKD along with marked hyperphosphatemia and hypocalcemia developed in these rats which led to arterial calcification and high bone turnover disease. Metformin protected from development toward severe CKD. Metformin-treated rats did not develop hyperphosphatemia or hypocalcemia and this prevented the development of vascular calcification and inhibited the progression toward high bone turnover disease. Kidneys of the metformin group showed significantly less cellular infiltration, fibrosis and inflammation. To study a possible direct effect of metformin on the development of vascular calcification, independent of its effect on renal function, metformin (200 mg/kg/day) or vehicle was dosed for ten weeks to rats with warfarin-induced vascular calcification. The drug did not reduce aorta or small vessel calcification in this animal model. Thus, metformin protected against the development of severe CKD and preserved calcium phosphorus homeostasis. As a result of its beneficial impact on renal function, associated comorbidities such as vascular calcification and high bone turnover disease were also prevented.

Metformin: A Candidate Drug for Renal Diseases.

Over the past decades metformin has been the optimal first-line treatment for type 2 diabetes mellitus (T2DM). Only in the last few years, it has become increasingly clear that metformin exerts benign pleiotropic actions beyond its prescribed use and ongoing investigations focus on a putative beneficial impact of metformin on the kidney. Both acute kidney injury (AKI) and chronic kidney disease (CKD), two major renal health issues, often result in the need for renal replacement therapy (dialysis or transplantation) with a high socio-economic impact for the patients. Unfortunately, to date, effective treatment directly targeting the kidney is lacking. Metformin has been shown to exert beneficial effects on the kidney in various clinical trials and experimental studies performed in divergent rodent models representing different types of renal diseases going from AKI to CKD. Despite growing evidence on metformin as a candidate drug for renal diseases, in-depth research is imperative to unravel the molecular signaling pathways responsible for metformin's renoprotective actions. This review will discuss the current state-of-the-art literature on clinical and preclinical data, and put forward potential cellular mechanisms and molecular pathways by which metformin ameliorates AKI/CKD.

Ligand trap for the activin type IIA receptor. The long-sought drug to overcome the calcification paradox in CKD?

The chronic kidney disease-mineral and bone disorder syndrome illustrates the association between a disturbed physiological bone turnover/mineralization and pathologic vascular mineralization; the so-called calcification paradox. This implies that treatments aimed at curing bone disorders might have serious implications for cardiovascular health and vice versa. Hence, there is an urgent need for treatments that are able to break through this cross-talk. Hereto, compounds such as those interfering with activin type IIA receptor signaling and acting upstream of the Wnt-ß-catenin pathway are of particular interest.

Can Intestinal Phosphate Binding or Inhibition of Hydroxyapatite Growth in the Vascular Wall Halt the Progression of Established Aortic Calcification in Chronic Kidney Disease?

Vascular calcification significantly contributes to mortality in chronic kidney disease (CKD) patients. Sevelamer and pyrophosphate (PPi) have proven to be effective in preventing vascular calcification, the former by controlling intestinal phosphate absorption, the latter by directly interfering with the hydroxyapatite crystal formation. Since most patients present with established vascular calcification, it is important to evaluate whether these compounds may also halt or reverse the progression of preexisting vascular calcification. CKD and vascular calcification were induced in male Wistar rats by a 0.75 % adenine low protein diet for 4 weeks. Treatment with PPi (30 or 120 µmol/kg/day), sevelamer carbonate (1500 mg/kg/day) or vehicle was started at the time point at which vascular calcification was present and continued for 3 weeks. Hyperphosphatemia and vascular calcification developed prior to treatment. A significant progression of aortic calcification in vehicle-treated rats with CKD was observed over the final 3-week period. Sevelamer treatment significantly reduced further progression of aortic calcification as compared to the vehicle control. No such an effect was seen for either PPi dose. Sevelamer but not PPi treatment resulted in an increase in both osteoblast and osteoid perimeter. Our study shows that sevelamer was able to reduce the progression of moderate to severe preexisting aortic calcification in a CKD rat model. Higher doses of PPi may be required to induce a similar reduction of severe established arterial calcification in this CKD model.